While anti-radiation suits or other protective gear may be effective at reducing radiation exposure, such gear is expensive, unwieldy, and generally not available to public. Moreover, radioprotective gear will not protect normal tissue adjacent to a tumor from stray radiation exposure during radiotherapy. Pharmaceutical radioprotectants offer a cost-efficient, effective and easily available alternative to radioprotective gear. However, previous attempts at radioprotection of normal cells with pharmaceutical compositions have not been entirely successful. For example, cytokines directed at mobilizing the peripheral blood progenitor cells confer a myeloprotective effect when given prior to radiation (Neta et al., Semin. Radiat. Oncol. 6:306-320, 1996), but do not confer systemic protection. Other chemical radioprotectors administered alone or in combination with biologic response modifiers have shown minor protective effects in mice, but application of these compounds to large mammals was less successful, and it was questioned whether chemical radioprotection was of any value (Maisin, J. R., Bacq and Alexander Award Lecture. “Chemical radioprotection: past, present, and future prospects”, Int J. Radiat Biol. 73:443-50, 1998). Pharmaceutical radiation sensitizers, which are known to preferentially enhance the effects of radiation in cancerous tissues, are clearly unsuited for the general systemic protection of normal tissues from exposure to ionizing radiation.
The major biological effects of radiation exposure are the destruction of bone marrow cells, gastrointestinal (GI) damage, lung pneumonitis, and central nervous system (CNS) damage. The long-term effects of radiation exposure include an increase in cancer rates. It has been estimated that the exposure of 100 rems (roentgen equivalent man: a measurement used to quantify the amount of radiation that would produce harmful biological effects) would produce ARS symptoms. Exposure levels above 300 rems would result in the death of approximately 50% of the exposed population.
The α,β-unsaturated aryl sulfones, in particular benzyl styryl sulfones, provide significant and selective systemic protection of normal cells from radiation-induced damage in animals. When used in radiotherapy techniques, these compounds also exhibit independent toxicity to cancer cells. These α,β-unsaturated aryl sulfones, in particular benzyl styryl sulfones, are described in U.S. Pat. Nos. 6,656,973 and 6,667,346, which are particularly incorporated herein by reference in their entirety. Although these compounds are stable in solid state their aqueous formulations for parenteral administration are pH sensitive and pose challenging hurdles to overcome physical stability. The most likely causative factor may be attributed to the reactive styryl sulfone conjugated double bond, which is prone to Michael addition by nucleophiles and eventual fallout of the conjugated addition product.
U.S. Pat. No. 6,656,973, describes in vitro pharmacological effects of DMSO solubilization of a benzyl styryl sulfone (e.g. ON 01210.NA) but fails to disclose a composition comprising ON 01210.NA formulation and specifically, a shelf stable formulation which is suitable for administration to humans.
PCT Application WO 2007/016201 describes pharmaceutical solution compositions for parenteral administration for reducing toxic effects of ionizing radiation in a subject, comprising an effective amount of at least one radioprotective α,β-Unsaturated aryl sulfone, and at least one component selected from the group consisting of a) a water soluble polymer in an amount between about 0.5% and about 90% w/v, b) at least one chemically modified cyclodextrin in an amount between about 20% and about 60% w/v, and c) DMA in an amount between 10% and about 50% w/v.
U.S. Patent Application 20090247624, and corresponding PCT Application WO 2008/105808, are directed to aqueous solutions, which comprise between about 20 mg/ml to about 100 mg/ml of at least one α,β-unsaturated aryl sulfone (e.g., the compound ON 01210.Na ((E)-4-Carboxystyryl-4-chlorobenzylsulfone sodium salt, a cosolvent in an amount between about 25% and about 90% w/v (e.g., about 50% PEG 400), wherein the composition is buffered and exists within the range of about pH 7.0 to about pH10 (e.g., 0.2M Tris-EDTA, pH about 8.5).
The aforementioned solution formulations have exhibited a sub-optimal shelf life and lack a preferred degree of solubility and/or stability. These formulations evolved progressively as a result of addressing the most challenging aspects in the formulation and drug development field, namely, solubility and stability parameters that defined the long term viability of these formulations. There seems to be a delicate balance between pH, solubility and stability of the active moiety in aqueous milieu, wherein achieving such balance and development of a shelf stable aqueous formulation has presented a formidable challenge. Therefore, a shelf stable effective solution formulation that prevents the breakdown of the therapeutically active entity and keeps the drug in the solution at the desired pH was most desired and significant effort was directed towards this goal.
What is needed therefore, is a shelf stable effective solution formulation of radioprotective α,β-unsaturated aryl sulfones that prevents the breakdown of the therapeutically active entity and keeps the drug in the solution at the desired pH. This invention solves these and other long felt needs by providing improved solution formulation of radioprotective α,β-unsaturated aryl sulfones having improved physical and chemical stability and enhanced shelf life.